You can get a pension forecast online now, so I did.  It seems that I have 7 years when I did not contribute enough, and those are of course the years when I was living in Spain... 

It never occurred to me that I should have carried on contributing during the period I lived abroad, and to do so would have cost a total of £4,422.35.  We did have that amount of disposable income available, but it was earmarked for DIY.  My husband's N.I. contributions were automatically credited to him, and this continued/continues wherever he lives, but mine were not.

In July next year I'll receive a state pension of £136.22 per week - see extra, whereas if I were fully paid up it would be £159.55 per week.  Since I reckon I would have to be claiming my pension for longer than 3.6 years to make it worth paying the back contributions, I'd better sort it out.  Having said that my state pension will be slightly more than I'm earning at B&Q (for 17.5 hrs), and that was my main concern.